Add MQTT backup reporting and trigger listener

.env.example

@@ -14,6 +14,15 @@ START_RETRIES=1
 LOCK_FILE="/run/lock/zorruno-docker-backup.lock"
 ZSTD_EXTRA_OPTS="-T0 -12"
 
+# Optional retained MQTT status and command listener settings.
+MQTT_REPORT_ENABLED=0
+MQTT_HOST="beaver"
+MQTT_PORT=1883
+MQTT_USERNAME="dockerbackup"
+MQTT_PASSWORD_FILE="/etc/zorruno-docker-backup/mqtt-password"
+MQTT_STATUS_TOPIC="viewroad-status/dockerbackup/beaver"
+MQTT_COMMAND_TOPIC="viewroad-commands/dockerbackup/beaver/run"
+
 # Rclone destination becomes <remote>/beaver/.
 RCLONE_ENABLED=0
 RCLONE_REMOTE="gdrive:dockerbackups"